Exploration of troposphere stratification



y .1950 L. J. SIVIAN 2,507,121

EXPLORATION OF TROPOSPHERE STRATIFICATION Filed June 27. 1946 sSheets-Sheet 1 RELAXA TIO N OSC/L L A TOR A T TOR/VEV May 9, 1950 J.SIVIAN EXPLORATION OF TROPOSPHERE STRATIF'ICATION 3 Sheets-Shet 2 FiledJune 27, 1946 lNl/ENTOR L.J.$/l /AN ATTORNEY mg mm 9, 19 L. J. SIVIANEXPLORATIGN 0F TROPOSPHERE STRATIFICATION 3 Sheets-Sheet 3 Filed June27, 1946 mm o MWQ INVENTOR L.J.5/l /AN ATTORNEY Patented May 9, 1950EXPLORATION F TROPOSPHE E STRATIFICATION Leon 3- Sivi u, Summ N. J a sinor to Bell Te ephone L bora ori Incorporated, N ow York, N. 1., acorporation of New York Application June 27. 1946, Serial No. 679,615 3Gl ims, 1.7'7- :2)

This invention relates to exploration of tropesphere stratification andmore particularly to methods of and systems for exploration oftropospheric and atmospheric conditions by means of compressional waves.

It has been found that discontinuities in the physical properties of theatmosphere may give rise to reflections of compressional waves, theintensity of which and the echo time interval of which may indicate thenature of the discon tinuity and measure its distance. Methods andapparatus for such explorations are disclosed and claimed in thecopending application of G. W. Gilman, Serial No. 676,611, filed June14, 1946, for Exploration of troposphere stratification.

An object of the present invention is to free indications received incompressional wave troposphere exploration from interfering effects suchas disturbing horizontally propagated sounds or horizontally propagatedreflections of the ex.-.- ploring energy.

Another object .of the invention is to enable discrimination againstreceipt of impulses arrive ing from higher regions of the atmosphere butnot vertically propagated.

A principal object of the invention is to enable a definitedetermination that an incoming compressional wave is being propagated ina vertical downward direction.

In accordance with one embodiment of theim vention a compressional wavesource isso designed and mounted as'to propagate compress-v sional wavesin a highly directive beam aimed at the region to be explored which, inthe particular embodiment of the invention disclosed, is the verticallyupward troposphere region. The compressional waves coursing upward aresent out in short pulses which are partially reflected at anydiscontinuity to return in a vertically downward direction to the regionof the compressional wave source. Two compressional wave receivers, alsohighly directive in their response to compressional waves, are sooriented as to receive only vertically downwardly pr pa ated energy andare located in the sound shadow of the directive com.- pr l w ve urce atthe transmitter so as o receive no ener y directly propa ated therefrom.These receivers are also substantially aligned in a vertical directionwith the lowermost li iently above he round to avoid ground ef: e tsupon the hori ntally p opa ated waves and with the uppermost at a fixeddistance above the lower vSufficiently great so that there is a cleanutseparation of the arrival times of a compres= sional wave propagatedvertically down-ward.

However, horizontally propagated interfering compressional wavesarriving either from an extraneous source or by complex paths from thelocal compressional wave transmitter will be simultaneously received bythe two receivers with substantially equal intensity. The two receiversmay have their outputs connected in opposition to the input .oi'anoscilloscope so that the effects upon the oscilloscope of horizontallypropagated waves will be substantially annulled.

In the drawing, Fig. 1 represents diagrammatically the circuit of oneembodiment of the invention and Figs. 2 and 3 show the circuits ofalternative embodiments.

Referring to Fig. 1 the variable frequency tone oscillator 10 isprovided with .a frequency varying element such as variable capacityelement 11 and is connected through the pulsing control loop l2 to theinput circuit of the amplifier l3 which feeds amplified tone current tothe vertically up.- wardly directed loudspeaker It to send sound en.-ergy toward the stratum or tropospheric discontinuity 15 directlyoverhead, The pulsing control loop 1 2 is normally short-circuitedthrough the shunt path 16 extending through the armature H of a relay t8having a winding l9 shunted by a variable resistor '20 to enableadjustment of the operating and release current of the relay. Arelaxation oscillator 2| has a space current path which passes throughthe winding i9 and resistor 20 and the periodicity of the oscillator 2!is ad justed in any well-known manner to accord with the. desiredperiodicity of the recurring pulses of sound energy to be propagatedupward to stratum l5, The length of each pulse will depend upon the timeduring which relay armature I! is separated from its lower contact whichin turn depends upon the adjustment of relay I8 and its shunt resistor20 and also upon the magnitude of the peak of space current of therelaxation oscillator.

At a shortdistance from the transmitter loud speaker It, a sound pickupdevice or microphone 23 is mounted at the focal point of a paraboloidalsound reflector 24 which is. highly selective for compressional wavespropagated vertically downward and which lies in the sound shadow of thehorn of the loudspeaker M. The microphone 23 which may be of theelectrodynamic or any other suitable type responds to incomingcompressional Waves and supplies electric currents of corre spondingfrequency and amplitude ever the connecting loop 25 to the input circuitof amplifier 26, the output circuit of which is I connected through thevariable hand filter 2"? to a rectifier 28 which is connected to astring oscillograph 29 to transmit thereto impulses corresponding torectified pulses of incoming compressional wave energy. Across the loopis connected a shortcircuiting path including the normally releasedarmature 30 actuated by relay winding 31 which with its sensitivityadjusting variable shunt resistor 32 is connected in series with therelay winding IS in the space current path of relaxation oscillator 2!.Accordingly, as th relay l8 operates to permit a pulse of tone currentto pass from tone oscillator It to amplifier l3 and loudspeaker !4 thewinding 3| is energized to actuate armature 38 short-circuiting loop 25to protect amplifier 26 from overload that might result from any casualdirect energization of the microphone 23 or the receiving circuitthereof by energy from loudspeaker It or its circuits. The armature 30should close the short-circuiting path before the directly propagatedenergy reaches microphone 23 and the path should stay closed until theimpulse from loudspeaker M has terminated. This may be effected byproper design and relative adjustments of the two relays at l9 and 3|and their variable shunt resistors but in practice a physical separationof suflicient magnitude between the loudspeaker l4 and microphone 23 maybe used to enable the actuation of the protecting armature 30 before thecompressional wave has time to traverse the physical space betweenloudspeaker l4 and microphone 23. The relay 3! should release a littletime after the termination of receipt of directly propagated energy sothat the receiving circuit of the microphone 23 may be prepared forincoming compressional wave energy arriving from the zenith inconsequence of reflection of vertically propagated waves from overheadatmospheric discontinuities. The refiected energy so received may beamplified by amplifier 26 and subjected to a, filtering action byvariable band-pass filter 21 to select a single tone or a narrowfrequency band which, after rectification by rectifier 28,'is utilizedtoactuate the string oscillograph or other wave recording device 29. Inorder to provide a marking pulse to denote the time of initiation of theupward compressional wave beam from loudspeaker Ill a path 35 leads fromthe input of the transmitter amplifier l3 to a potentiometer 36 to whichan amplifier 31 is connected. The amplifier 3'! has an output circuitleading to the input of receiver amplifier 26 and serves as anasymmetric translator to preclude transmission from the input circuit ofamplifier 26 to the input circuit of amplifier l3. It'follows that theactuation of relay Hi to permit'a pulse of tone energy to energizeloudspeaker l4 also permits a marking pulse to pass by way of path 35,potentiometer 36 and asymmetric device 31 to the receiving amplifier 26to be filtered, rectified and finally recorded at oscillograph 29 as thepip T1. During this time and for a short time thereafter the output pathof microphone 23 remains short-circuited. When the compressional beamenergy from loudspeaker l4 reaches discontinuity IS, a portion of it isrefiected and impinges upon microphone 23 to cause the recording of thepip T2. The oscillograph record may be calibrated as indicated so thatthe time incidence of each pip is shown as well as the If desired, the

described is disclosed in the G. W. Gilman application, Serial No.676,611 to which reference previously has been made. However, thepresent invention involves an improvement upon that system to enablediscrimination against energy arriving from unwanted sources anddirections and to preclude giving a false or deceptive indication. Forthis purpose the receiving station may be provided with a secondmicrophone 38 located slightly to one side of microphone 23 by a lateraldistance a so as not to interfere with vertically downwardly directedenerg to be received by microphone 23. The microphone 38 is mounted atan elevation substantially higher than microphone 23 by an altitudedifierence hi sufiicient to cause a clearly distinguishable advance inarrival time of a reflected pulse from discontinuity l5. The microphone38 is provided with a paraboloidal reflector 39, the assemblage beinghighly directive to receive vertically downwardly propagatedcompressional waves' and to discriminate against compressional wavesarriving from other directions. The circuits and apparatus associatedwith microphone 38 may be otherwise identical with those connected tomicrophon 23.

It will be apparent that when the marking pulse is transmitted over path35 it will divide,

part going to potentiometer 41, asymmetric device d8, the input ofamplifier 40, hand filter 4| and rectifier 42 to produce a pip T3 on therecord of string oscillograph 43 which will be in time coincidence withpip T1 on the record of oscillograph 29. At that time relaywinding 44 isoperatedv to close the protective shunt path through its armature 45.When the reflection from discontinuity |5 reaches microphone 38 theprotective short circuit has already opened so that there is recorded apip T; which will occur at a time in advance of pip T2 correspondingsubstantially to the transit time for compressional waves over thedistance hi. This assures the observer that the indications are from avertically downwardly propagated Wave. If, however, horizontallypropagated noise, as from a gun shot, ar-

rives at microphones 23 and 38 it will produce pips which are in timecoincidence or at least differ only by the transit time over distance awhich is made the minimum possible which Willi avoid Vertical alignmentof the two reflectors velope pulse of oscillations which may lie in theaudible range or may even be supersonic. The choice of the pulseduration while not critical involves several factors. The pulse must belong enough for the time constants of the transmitting and receivingcircuits to admit of a pulse envelope which is essentially flat-toppedwith vertical sides. the minimum height from which a reflection may bereceived and observed without interference from the sender decreases.duration increases the ratio of the desired reflected pulse to thebackward scattering of sound by the great mass of inhomogeneities in theair decreases. For a frequency of 2000 cycles per second the pulseduration may be from 30 to 45 milliseconds; for a frequency of 6000cycles per second it may be 10 to 15 milliseconds.

The system of Fig. 2 involves a transmitter identical with that ofFig; 1. At the receiver,

however, the rectified output pulses .are impressed As the pulseduration is increased Also, as the pulse in opposing relation upon the.input circuit of the single string oscillograph 50. The compressionalwave receiving system also diffiers from that of Fig. 1 in that themicrophones 5i and 52 are vertically aligned so that the paraboloidalreflector 53 is in th shadow of the reflector 5 5. However, if theseparation in elevation he sllfil cient vertically downwardly propa atedcompressional wave energy will reach microphone 52 by diffraction,

In operationthe elements of Fig. 2 function as the similarly designatedelements of Fig. i. Actuation of relay it sends a pulse of tone cur rentfrom source to loudspeaker It and a simultaneous mar-king pulse to thepath 35.. However, the potentiometers .36 and s1 are adjusted inconjunction with their respective amplifiers '31 and 48 to transmitpulses of diiierent magnitudes and the outputs of rectifiers 28 and 42are poled in opposition to cause the rectified pulses to be of opposingsign, as indicated by the broken lines at T5, to yield a resultantmarking pulse as indicated in the solid line. Any simultaneouslyreceived energy coming from a horizontal direction reaches microphones5i and 52 simultaneously to produce opposing pulses, as at T6, with noresultant indication. However, the echo or return pulse received fromvertically aloft arrives first at microphone 5| to produce pulse T7 and,subsequently, at microphone 52 to produce the reversely directed pulseT8. The spacing of pulses T7 and T8 gives definite assurance that theyare occasioned by an echo from the troposphere.

Fig. 3 combines the indicating expedients of both Fig. 1 and Fig. 2 atthe receiver. As in the case of Fig. 2, similar elements are similarlydesignated and the vertically aligned positioning of microphones 56 and51 is like that of Fig. 2 as is also the adjustment of potentiometers 58and 59. Three oscillographs are employed. The first indicated at 6!] isconnected to the input circuit of rectifier 42 and, accordingly,indicates marking oscillations, extraneous oscillations and troposphereecho oscillations by tone frequency oscillograms at T9, T10 and T11,respectively. A second oscillograph Si is provided with two strings toproduce two separate oscillograms in connection with a single scale thuscombining in a single instrument the functions of the two oscillographs29 and 43 of Fig. 1 to show by comparison the simultaneous arrival ofthe marker pulse and the earlier arrival of the echo pulse at the moreelevated microphone. A third oscillograph 62 is in all respectsidentical with the oscillograph 50 of Fig. 2. It is thus possible to seejust how far away is the overhead discontinuity of the troposphere andto ascertain if extraneous pulses are being received from horizontal orother undesired directions.

What is claimed is:

1. A system for producing an indication of impedance discontinuities inthe atmosphere which comprises a source of ultra-sonic frequencyelectric energy, a directive translating device to convert said electricenergy to compressional wave energy and to direct said wav energyvertically toward the troposphere in a narrow beam substantiallysymmetrically disposed about a vertically directed axis, a. pair ofreceiving devices to receive reflected portions of said verticallytransmitted compressional wave energy and to translate said receivedenergy into electrical energy, said receiving devices each having ahighly directive lobe of energy reception substant al y symmetrica ydispos about a in s h pace sep ra ion hat vertically refle ted.

n r y is received by em pe ceptible se q es, amplifying means andunilaterally-sow duct ng rect fy ng means conn cted series to the outputof e ch of said receiving devices, an scilloscope responsive to anapplied electro m tive force to produce a timare atcd visual in ati n osaid applied electromot ve force, an c lt means interconnec ing th ou puof said t fyin devices in oppo ed polarity to the same terminals on saidoscilloscope, means for periodi, cally delivering energy from saidsource to said directive translating device for transmission toward thetroposphere and means to pro uc on said oscillo cope a visual indi ationof the time occurrenc of each energy transmission toward saidtroposphere, said means comprising circuit means interconnecting saidsource of electric energy and at least one of said amplifying andunilaterally-conducting rectifying means to deliver to said oscilloscopea pulse of unidirectional electromotive force at the time of each energytransmission toward the troposphere.

2. A system for exploring the troposphere which comprises a periodicallyactivated source of electric wave energy, a compressional wavetransmitter connected thereto and having a highly directive lobe ofenergy distribution to direct said energy toward the troposphere in anarrow beam substantially symmetrically disposed about the longitudinalaxis of said beam, a pair of compressional wave receivers each having ahighly directive lobe of energy reception, said lobe being substantiallysymmetrically disposed about the longitudinal axis thereof, saidreceivers being positioned one above the other in space separation withthe lobe axis of each aligned and substantially parallel to the lobeaxis of said transmitter, such that the incidence upon them of energyreflected from the troposphere is in perceptible sequential relation,amplifying and translating means individual to and connected to each ofsaid receivers to convert received compressional wave energy into a.unidirectional electromotive force, indicating means operative inresponse to an applied electromotive force to produce a visualindication of the time of application of said force with respect to areference time condition, circuit means connecting the output of each ofsaid translating means to said visual indicating means in opposedpolarity, and circuit means of unequal signal level interconnecting saidperiodically-activated source of wave energy and said amplifying andtranslating means to deliver to said indicating means unequal-amplitudepolarity-opposed pulses of said electric wave energy at the time of eachtransmission of compressional wave energy toward the troposphere by saiddirective transmitter.

3. A system for tropospheric explorations which comprises a source ofelectric wave energy, a transmitter connected thereto to translate andtransmit said electric Wave energy in a highly directive lobe ofcompressional wave energy substantially symmetrically disposed about thelongitudinal axis of said lobe, means for periodically activating saidelectric source for intermittent short periods, a pair of compressionalwave receivers each having a highly directive lobe of energy receptionin substantially symmetrical distribution about the longitudinal axis ofsaid 76 lobe, said receivers being located vertically one above theother in space separation such that the lobe axis of each is insubstantial alignment and parallel to the lobe axis of said transmitterand vertically-reflected energy incident thereon is received inperceptible sequential relation, unidirectionally conducting and.translating means connected to each of said receivers to convert saidreceived energy into a pair of unidirectional electromotive forces,indicating means responsive to an applied electromotive force to producea visual indication of the time of application thereof with reference toa reference time, circuit means connecting the outputs of saidtranslating means to said oscilloscope in opposed polarities, andcircuit means of unequal signal level interconnecting said periodicallyactivated source and said translating means to produce a referencedeflection on said oscilloscope at the instant of each energytransmission toward the troposphere.

LEON J. SIVIAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

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